The present invention relates to control systems for a printing press.
In the past, a paper web has been unwound from a roll, and passed through the cylinders of a printing press for printing the web. When moisture, such as ink or other fluids, is applied to the web during printing, the web absorbs the moisture and laterally fans out, such that the side margins of the web are increased in dimensions between opposed edges of the web. Other factors which may contribute to the fanning out of the web are paper formulation, stretch, printing compression, tension, dampening fluid, and convection drying.
As a result, the web width of increased lateral dimensions may cause misregistration of the web in the printing units of the press, causing a fault in the location of inks subsequently applied to the web, such as on multi-colored printing press.
Some attempts have been made to correct the fanning out of the web. First, a rotatable wheel has been applied to a central portion of the web intermediate the side edges of the web in order to tighten the web 10. The wheel is preferably located adjacent a nip between opposed blanket rolls which apply an ink image to the web. However, it has been found that if too much pressure is applied by the wheel, the web may become ruptured, which is an undesirable result. It has also been attempted to direct a stream of air against a surface of the web to laterally shorten the web. However, both the wheels and air streams require careful adjustment by the operator in order to achieve the desired result, particularly since the devices are preferably placed very close to the nip between the blanket rolls, thus posing possible harm to the operator unless the press is stopped. Thus, these devices are tedious to use, and contribute significantly to undesirable down time of the press in order to perform these adjustments.